1. Field of the Invention
This invention relates generally to tape editing systems, and more particularly is directed to improvements in tape editing systems of the type having a first or master VTR for reproducing video signals recorded on a first tape and a second or slave VTR selectively operable in a playback mode for reproducing video signals previously recorded on a second tape or in a record mode for replacing a portion of such previously recorded signals with a portion of the video signals being simultaneously reproduced from the first tape.
2. Description of the Prior Art
An existing tape editing system of the above described type is provided with an editing control unit having first and second counters for counting control pulses or addresses previously recorded along the first and second tapes, respectively. In using the existing editing control unit, an operator observes an image produced on a monitor associated with the master VTR by the video signals reproduced from the first tape during a relatively slow or search forward movement of such tape, and, at the selected cut-in address or point, that is, the commencement of the portion of such video signals which are to replace a portion of the video signals on the second tape, the operator halts the forward movement of the tape and re-sets the first counter to zero. Then the first or master VTR is operated in its rewind mode, that is, the first tape is moved in its reverse direction, and the first counter counts down from zero for measuring a predetermined distance along the first tape from the selected cut-in address to a stand-by address at which the reverse movement of the first tape is halted by a signal from the first counter. The cut-in address on the second tape is similarly selected by the operator who, at such address, re-sets the second counter to zero and then causes the second or slave VTR to effect reverse movement of the second tape until the second counter halts such reverse movement at a stand-by address which is the same predetermined distance in the reverse direction along the second tape from the respective cut-in address. Thereafter, operation of both VTRs in the playback mode is initiated simultaneously starting with both tapes at the stand-by addresses thereof and with both VTRs under the control of the same external synchronizing signals so that the first and second counters count up to zero at the same time to provide a cut-in signal by which the second or slave VTR is changed-over to its record mode for recording on the second tape the video signals being reproduced from the first tape. During such recording of video signals on the second tape, at which time both tapes are being moved forwardly at the normal speed for recording and reproducing operations, the operator observes the monitor associated with the master VTR and, at a selected cut-out address or point, that is, the end of the portion of the video signals being reproduced from the first tape which are to replace a portion of the video signals previously recorded on the second tape, the operator manually changes-over the second or slave VTR from its record mode back to its playback mode.
The above described existing tape editing system permits the relatively accurate selection of the cut-in addresses on the first and second tapes, respectively, as such cut-in addresses can be selected during the relatively slow or search forward movement of the respective tapes. However, the cut-out point or address has to be selected during the normal forward movement of the tapes at the standard speed for recording and reproducing operations which is substantially greater than the search speed. Therefore, the cut-out point, which is also important in effecting the precise editing of the second or slave tape, cannot be accurately selected and, as a result, the edited tape may have undesired video signals recorded thereon. Moreover, in selecting the cut-in point or address on each of the tapes, the operator has to first halt the forward movement of the tape at the selected address and then reset the selected counter to zero, that is, a two-step operation is required in selecting each cut-in address, and the inertia of the tape drive may make it difficult to halt the tape movement with the tape precisely at the desired cut-in address. Furthermore, no provision is made in the existing tape editing system for correcting the selected cut-in address other than by the relatively tedious repetition of the above described procedure for establishing the cut-in address.